1. Field of the Invention
The present invention relates to a vehicular anti-skid brake device in which the control of a braking force of a braking device relative to the wheels, even if a control device for suppressing the braking force should malfunction while braking is not applied, there occurs no interruption in the braking operation of the braking device when braking is applied due to such malfunction of the control device.
2. Description of Prior Art
If the braking input to a wheel is excessive when rapid braking is applied to the vehicle, the wheel becomes locked, resulting not only in a lowering of the braking efficiency but also loss of directional stability and steering of the wheel, which is very dangerous. A so-called anti-skid brake device has been proposed for prevention of such a dangerous state.
A hydraulically-operated vehicular braking device provided with an anti-skid control device generally comprises a brake oil chamber for receiving brake oil pressure generated in accordance with the braking operation, and a control oil chamber for receiving control oil pressure against brake oil pressure when the braking force to the wheels is excessive. The device is so designed that when brake oil is introduced into the brake oil chamber, pressing frictional contact members such as a brake pad, brake shoe or the like are brought into frictional contact with rotary members such as a brake disk, brake lining or the like which rotate integral with the wheels, to be pressed so as to produce a braking torque, and when the braking torque at that time, that is, the braking force is excessive, control oil is introduced into the control oil chamber, and as a consequence, the pressing frictional contact member moves back from the rotary member.
Incidentally, if the control oil is introduced into the control oil chamber as a result of malfunction of the anti-skid control device when braking is not applied, a spacing between the pressing frictional contact member and the rotary member becomes greater than in normal condition so that the distance of movement of the pressing frictional contact member required for braking becomes greater than that in the normal case. Therefore, when the braking operation is effected in that state, the braking effect is different from that of the normal case, and the time at which the braking force is produced is delayed or there also occurs the possibility of not sufficiently producing the braking force as the case may be.
It can be said that there is total absence of possibility for the anti-skid brake device to undergo malfunction due to vibrations or shocks during travel of the vehicle or other causes. For these reacons, it is desirable that the anti-skid brake device is designed so that even if the anti-skid brake device should malfunction, the braking operation of the braking device would not inconveniently be affected thereby. In the past, anti-skid brake devices suited for the purposes noted above have not been proposed.